The Amp Garage

The .3 ohm measurement was taken in circuit but with the tubes and pilot light removed. Center tap was initially tied to the cathode bias resistor, fully bypassed with a 250uF cap. I also tried it at chassis ground and a voltage divider at +100v with no audible change. If a high resistance center ta...

Well that's something I didn't even consider... I measured resistance from CT to either phase with a good ol fluke mm. Measured .3 ohms on both and figured hey, shes balanced. Just went back and measured phase to phase with the CT floating and also measured .3 ohms. Then shorted my meter probes toge...

That must be the case here, I've just never run into such an extreme case. Grounded heater CT is only marginally quieter than leaving it floating. Resistive artificial CT is whisper quiet!

And yes, that is a great reference that i find myself going back to quite often!

Cheers!

Ran into an oddball issue with my latest build, and figured I'd rant about it here and see if anyone else has run into a similar issue! I've been working away on an AC30 TB inspired build using a hammond 270HX for the PT and a recycled yba1 output transformer. Went overboard on layout and grounding ...

You know rangkipkin, I can find space for a hand circular saw, and it seems that right there could make the work of cutting that freegan angle much more quick, efficient and accurate than I can with a good hand saw. I will be looking into that, Thanks man, Phil cheers! Take yer time with measuremen...

yes sir you got er. precision measurement and a very flat, straight guide clamped solid. Circular saw works wonders but can be intimidating if you are unfamiliar, its basically a handheld table saw! I use a big 16" blade and its still a bit scary to fire up, but can cut a 6x6 post in a single pass.

old industrial scorched earth method of PCB cloning; depopulate the board and scan it along with a precision scale in the X and Y axes, import the scanned image into AutoCAD and adjust to real world units using the scale references. Then manually create polylines over the traces from the image. Prec...

20th anniversary series. They must have wanted to throw a big party every 5 years over there! I recall working on one of the 100W 2210s a few years back, the lead tones crush the jubilee IMHO.

you're a few years early for the jube (made in 1987), the last two digits of the serial put er to a 1984 jcm800 2205. Still a great machine, has its own flava!

I've had success with a 16" circular saw and a good straight edge. Definitely leave a little meat on that bone and finish by hand with sandpaper.

If you can hold your hand on it without screaming, its ok!

I'd lean towards a 4xEl84, fixed bias power amp with presence and resonance controls. Use a good Marshall style 50W OPT, hammond 290LX power tx, 3H choke... TMB tone stack... heck just build a low voltage JMP with 4xel84 at this point!

too many thingys! im a one or two thingy kinda cat!

whatever happened to "point the thingee to where the sound is most goodest"?

You have exorcised the demons! Full out cathode bias with no NFB and a somewhat gainy preamp tends to be the worst case scenario for fighting hum, nicely done!